Navigation System Flashcards
IRS
How long for FAST Realign?
30 Seconds
Which IRU’s remain powered when AC power is lost?
Left and Center (Right limited 5 min)
What lights will illuminate on the L, C, R IRU advisory lights?
Left remains dark, C-ON DC and the R will be ON DC for 5 minutes
How many IRU’s?
3
How do you ALIGN the IRU’s?
Switch to NAV.
How long does the alignment process take?
Alignment takes about 10 minutes.
How can you tell how much longer until alignment is complete?
HDG counts down from 7 minutes.
What is the initialization priority?
GPS position,
Gate position,
LAST position and ARP.
Otherwise put in the LAT/LONG for the Gate Position,
then ARP.
What does Flashing Lights on the IRU mean?
It happens after 10 minutes for one of 3 reasons:
1. No position entered
2. significant difference between previous position and entered position
3. the aircraft was moved during ALIGNMENT.
How can you force in a position?
On the third attempt, it will accept the position you entered.
You might do this if an IRU was replaced.
What does a FAULT light indicate?
A FAULT
How is a HEADING entered into the IRU?
Headings should populate automatically, but If a FAULT light occurs, the QRH has us select ATT.
IF the FAULT light extinguishes, we can enter a HEADING via the IRU Control panel, or the FMS POS INIT page.
On the IRU panel, press H, and enter the heading.
Why does the ON DC illuminates momentarily during power up?
Part of self test
If the ON DC light illuminates after power up, what does this mean?
- normal AC power to the IRU has failed
- The IRU is operating on DC power from the HOT BAT bus
NOTE: On the ground, a Ground-Call Horn sounds in the nose wheel well.
IRU ALIGN light stays on for 30 seconds during shutdown, why?
Part of the shutdown process and the IRU is saving the LAST POS.
